Question

在我的房间应用程序中，我从工作良好的new_pb字段开始。我现在正在尝试添加pb_value和pb_details，但是这些字段未在模拟器上显示。另外，当我尝试输入新的pb时，什么也没有出现。它仅显示已在数据库中创建的数据库。已添加迁移并更新了版本号。

MainActivity

class MainActivity : AppCompatActivity() {

    private val newPbActivityRequestCode = 1
    private lateinit var pbViewModel: PbViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val toolbar = findViewById<Toolbar>(R.id.toolbar)
        setSupportActionBar(toolbar)

        val recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
        val adapter = PbListAdapter(this)
        recyclerView.adapter = adapter
        recyclerView.layoutManager = LinearLayoutManager(this)

        pbViewModel = ViewModelProviders.of(this).get(PbViewModel::class.java)

        pbViewModel.allPbs.observe(this, Observer { pbs -> pbs?.let { adapter.setPbs(it)}})

        val fab = findViewById<FloatingActionButton>(R.id.fab)
        fab.setOnClickListener {
            val intent = Intent(this@MainActivity, NewPbActivity::class.java)
            startActivityForResult(intent, newPbActivityRequestCode)
        }
    }
    override fun onActivityResult(requestCode: Int, resultCode: Int, intentData: Intent?) {
        super.onActivityResult(requestCode, resultCode, intentData)

        if (requestCode == newPbActivityRequestCode && resultCode == Activity.RESULT_OK) {
            intentData?.let { data ->
                val new_pb = NewPb(data.getIntExtra(
                    NewPbActivity.EXTRA_REPLY, 0),"", 0.0,  "")
                pbViewModel.insert(new_pb)
            }
        } else {
            Toast.makeText(
                applicationContext,
                R.string.empty_not_saved,
                Toast.LENGTH_LONG
            ).show()

NewPbActivity

class NewPbActivity : AppCompatActivity() {

    private lateinit var editNewPb: EditText

    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_new_pb)
        editNewPb = findViewById(R.id.edit_new_pb)

        val button = findViewById<Button>(R.id.button_save)
        button.setOnClickListener {
            val replyIntent = Intent()
            if (TextUtils.isEmpty(editNewPb.text)) {
                setResult(Activity.RESULT_CANCELED, replyIntent)
            } else {
                val new_pb = editNewPb.text.toString()
                replyIntent.putExtra(EXTRA_REPLY, new_pb)
                setResult(Activity.RESULT_OK, replyIntent)
            }
            finish()
        }
    }
    companion object {
        const val EXTRA_REPLY = "com.example.android.NewPblistsql.REPLY"


    }
}

Answer 1

如果您的数据库已经使用table创建，那么要将新字段添加到现有表中，您需要在会议室迁移块中触发等效于onUpgrade（）的alter query。如果需要的话，请转至Android开发者网站进行房间迁移。

Answer 2

更改数据库版本，以便您调用并执行类似的操作

 @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  db.execSQL("DROP TABLE IF EXISTS " + TBL_GPS_DATA);
 this.onCreate(db);//OP1
//OR OP2 alter table
 try {
            if (newVersion > oldVersion) {
//                db.execSQL("ALTER TABLE " + TBL_GPS_DATA + " ADD COLUMN " + COUNTRY + " TEXT DEFAULT 'INDIA'");
//                db.execSQL("ALTER TABLE " + TBL_GPS_DATA + " ADD COLUMN " + COUNTRY_FLAG + " TEXT DEFAULT '0' ");

                db.execSQL("ALTER TABLE " + TBL_GPS_DATA + " ADD COLUMN " + COUNTRY + " TEXT ");
                db.execSQL("ALTER TABLE " + TBL_GPS_DATA + " ADD COLUMN " + COUNTRY_FLAG + " TEXT ");
            }
        } catch (Exception e) {
            System.out.println("this is error due to onupgrade v ");
        }
}

Room：模拟器上未显示其他字段

2 个答案: